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Severe weather episode June 20-21

June 21, 2013

Severe weather episode June 20-21

A Mesoscale Convection System (MCS) brought severe weather to the
state overnight during Thursday and Friday this week (June 20-21). This
complex of thunderstorms produced some hail that ranged from 1 inch to
one and three-quarter inch diameter, along with some wind gusts from
60-85 mph, especially in western and central parts of the state where
many trees were damage. There were numerous power outages reported,
along with some very heavy rainfalls that caused flash flooding in a
several Minnesota counties. Many roads were closed for a time. Some of
the rainfall amounts reported included:
3.56" at Hawley
3.41 inches at Sandstone
3.73 inches at Little Falls
2.63 inches at Brainerd
2.57 inches at Cloquet
2.25 inches at Staples

Yet more rain with warm air and high dewpoints is forecasted for the upcoming weekend across Minnesota.

New Seasonal Climate Outlook

The NOAA Climate Prediction Center released a new seasonal climate
outlook on Thursday this week, covering the period from July through
September. The western USA is expected to be warmer than normal while
much of the rest of the country, including Minnesota sees equal chances
of being warmer or cooler than normal during the ENSO neutral period.
The southeastern USA is expected to be wetter than normal over this
period, while the northwest and parts of west Texas and Oklahoma are
expected to be dry. For much of the country, including Minnesota, the
outlook shows equal chances for wetter or drier than normal. Certainly
our recent summer climate trends suggest we'll see both wetter and drier
than normal conditions prevail, but in different parts of the state.

90s F Return

Thursday, June 20 brought plenty of heat and moisture to the state as
dewpoints rose into the low to mid 60s F and late afternoon temperatures
reached 90 degrees F at many locations including Red Wing, Luverne,
Marshall, Worthington, Mankato, Olivia, and Jackson. The Twin Cities,
along with St James and Willmar reported a high temperature of 91
degrees F. This was the second episode of 90s F in 2013 for many
southern Minnesota observers, and the warmest day since the
record-setting high temperatures of May 14 last month. The high
dewpoints provided fuel for thunderstorm development and some of the
state was under a flash flood watch going into Friday, June 21st. Some
of these Minnesota cities under a flash flood watch were Duluth,
Cloquet, and Two Harbors, all of which suffered from the devastating
floods of almost exactly one year ago.

June 21st Summer Solstice Frost of 1992

This date is a memorable one in Minnesota history as the only summer
solstice that brought damage frost to the state's corn and soybean
crops. The Mt Pinatubo eruption in the Philippines during 1991 was
later attributed to be one of the causes of this event which turned out
to a singularity in Minnesota's climate history. Temperatures as cold
as 25 degrees F (Brimson) were reported in the north, but even as far
south as Preston, Theilman and Zumbrota reported 33 degrees F with frost
in low spots. Some corn fields were severely damaged and later only
harvested for silage. Soybeans leaves mostly burned by the frost
recovered and produced even pods and beans for harvest, but the yields
were not very good.

Weekly Weather potpourri

Tropical Storm Barry was producing heavy rainfall amounts over parts
of central Mexico this week. Some areas had received 3 to 5 inches of
rainfall in a short period of time. But Barry was slowly dissipating by
Friday of this week.

Tropical Storm Bebinca was tracking toward
Vietnam this week packing 50-60 mph winds and producing sea wave heights
of 15 to 20 feet. It was expected to bring heavy rains to Hanoi over
the weekend as it dissipates over land.

Calgary, Canada was hit
with a major flooding this week of nearby rivers and streams as a large
scale storm system brought six or more inches of rainfall to some areas.
It was some of the worst flooding there in a decade and caused the
evacuation of up to 75,000 citizens due to the threat of high water.

MPR listener question

Since this week was the one-year anniversary of the devastating
flash floods in Duluth, Two Harbors, and Moose Lake I wondered how the
maximum rainfall intensity of that storm compared to the famous Twin
Cities flash flood of July 23, 1987 (10 inches in 6 hours)?
Answer:
The USGS has just finished a thorough report of the flash flood in
northeastern Minnesota over June 19-20, 2012. It is available online.

Comparing maximum rainfall rates of the two storms is approximate, not
precise. But the data suggest that the maximum intensity during the
Twin Cities flash flood of July 23, 1987 ranged from 2.5 to 3.0 inches
per hour. Analysis of the overnight rainfall rates from the June 19-20,
2012 flash flood in the Duluth area last year suggest that maximum
rainfall rates ranged from 2 to 4 inches. These are remarkable
intensities, perhaps on the order of once in 100 or 200 year rainfall
rates, and certainly analogous to those measured during powerful
tropical storms.

Twin Cities Almanac for June 21st

The average MSP high temperature for this date is 79 degrees F (plus or
minus 8 degrees F standard deviation), while the average low is 60
degrees F (plus or minus 7 degrees F standard deviation).

MSP Local Records for June 21st

MSP weather records for this date include: highest daily maximum
temperature of 95 degrees F in 1910; lowest daily maximum temperature of
59 degrees F in 1906; lowest daily minimum temperature of 39 F in 1992;
highest daily minimum temperature of 74 F in 1943; and record
precipitation of 2.95 inches in 2002; No snow has been recorded on this
date.

Average dew point for June 21st is 56 degrees F, with a maximum of 75 degrees F in 1986 and a minimum of 26 degrees F in 1992.

All-time state records for June 21st

The state record high temperature for this date is 107 degrees F at
Browns Valley (Traverse County) in 1988. The state record low
temperature for this date is 25 degrees F at Sawbill Camp (Cook County)
in 1936 an at Brimson (St Louis County) in 1992. State record
precipitation for this date is 6.25 inches at West Union (Todd County)
in 1941; and no snow has fallen on this date.

Past Weather Features:

June
21, 1988 was the hottest in Minnesota history bringing temperatures of
90 degrees F or greater to over 100 cities in the state. Many observers
reported record-setting high temperatures of 100 degrees F or greater,
including nearly all the climate observers in southwestern counties.
June of 1988 proved to be the 2nd warmest in state history, with
numerous days over 90 degrees F.

June 21, 2009 brought three
tornadoes to Faribault County and one to Freeborn County. These
tornadoes occurred between 7:00 pm and 8:30 pm and all were on the
ground for less than 2 miles. Little damage was reported. These four
were among only 24 tornadoes reported that year in Minnesota.

Outlook

Warmer than normal temperatures with high dewpoints over the weekend
along with chances for showers and thunderstorms, some of which could be
heavy. Continued warm and humid into early next week with chances for
thunderstorms.